B2 Topic 1- Inside Living Cells (Edexcel GCSE Additional Science)

Topic 1 of Biology Edexcel additional science

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  • Created by: Laura
  • Created on: 06-11-11 14:09


  • Respiration is NOT breathing in and out
  • Carbon dioxide is the product of aerobic respiration
  • Respiration happens in ALL living organsims

Aerobic respiration

Glucose+ Oxygen ==> Carbon Dioxide+ Water (+Energy)

Diffusion is where a substance moves from an area of high concentration to an area of low concentration. We say that the substance moves down a concentration gradient. 

Anaerobic respiration

Glucose==> Lactic Acid (+Energy)

Advantage: Helps an organsim to survive at times of low oxygen levels

Disadvantages: Only lasts a short amount of time, produces lactic acid (poisonous), produces less energy that aerobic respiration. 

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Not all weight loss diets are scientifically proven or recommended (for health reasons)

The UK government recommend you do 30 minutes of excercise 5 times a week; this has increased since 2004 because more scientific papers have been published which prove that you need more exercise to prevent heart disease, diabetes and high cohlesterol. 

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DNA and protein synthesis

A DNA molecule is a double helix shape 

There are 4 different bases in a DNA molecule 

Adenine and Thymine (which pair up using a double hydrogen bond)

Cystosine and Guanine (which pair up using a triple hydrogen bond)

A gene codes for a protein         A triplet codon codes for an Amino Acid

A DNA has certain genes "switched on" in each cell which determines which proteins are created.

A polypetide is a chain of amino acids. 

Protein synthesis- DNA is unzipped by an enzyme, Complementary mRNA molecules join up and when reach end of gene leave the nucleas. mRNA joins onto ribosome where tRNA joins on. tRNA has amino acids attached which join together to create proteins. 

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Using Microorgansims

Yeast is used to make bread rise. When yeast respires aerobically it produces carbon dioxide which makes the bread rise.                                                  Bacteria are put into milk which uses the sugar lactose (in the milk) to respire. The bacteria turn the lactose into lactic acid and the increased acidity curdles the milk- turning it into cheese. 

An example of an anitbiotic is penicillin. 

Microorgansims can be used to produce human insulin. The gene for human insulin is cut out of the DNA and is placed into a plasmid (bacteria's DNA). This plasmid is placed back into the bacteria and is cultivated for diabetes sufferers use. 

Mycoprotein is used for food. Using microorganisms for food production is faster, easier to look after, can be produced anywhere in the world, can use the waste products of farming for production, cheaper. 

Fermenters need aseptic conditions to ensure no other microorganisms are growing in there. 

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